1. Field of the Invention
This invention relates to a parenterally administratable composition containing a 16-phenoxy prostaglandin and polyethylene glycol having a molecular weight from 380 to about 630 which is useful as an abortifacient.
2. Prior Art
The compounds which are useful in the composition of this invention are disclosed and described in U.S. Pat. No. 3,985,791, issued Oct. 12, 1976 to Muchowski and Fried. It is also known that certain prostaglandins, for example, PGE.sub.1, PGE.sub.2, PGA.sub.2 or the 15-keto, 15-methyl, 15-hydroxy or 3-oxa derivatives, possess tranquilizing activity and can be mixed with polyethylene glycol 400 and powdered polyethylene glycol 6000 to give orally administratable lozenges.
Prostaglandins are often unstable, and several solutions to solving this stability problem have been proposed. See for example 4,011,313 to Thompson which relates to a stabilized prostaglandin composition which employs a dialkylated mono- or polyalkylene glycol. It is also known that the prostaglandin PGE.sub.1 can be made into a topical cream suitable for the treatment of psoriasis by mixing with polyethylene glycol 400, a polyethylene glycol 4000 and 1,2,6-hexanetriol.
We have now discovered that dl-9.alpha.,11.alpha.,15.alpha.-trihydroxy-16-phenoxy-17,18,20-tetranorpro sta-4,5,13-trans-trieneoic acid and the lower alkyl esters of 1 to 4 carbon atoms thereof, when mixed with a polyethylene glycol having a molecular weight of 380 to about 630, can be subcutaneously injected into a mammal and exhibits release rate much lower than would be expected and thus allows for prolonged activity of the prostaglandin.